Oscillating screen

ABSTRACT

Device for the classification of solid objects of the oscillating screen type. In operation the oscillating screen is gradually pulled down against the action of springy means. From the lowermost position the screen is released and receives an upward thrust which is abruptly interrupted by stop means, whereby the screen is unclogged.

ilnited States lPatent [191 Pellet i [54] OSCILLATING SCREEN [75] Inventor: Ron Feller, Ramat-Gan, Israel [73] Assignee: `The State of Israel, Ministry of Agriculture, Jerusalem, Israel [22] Filed: Apr`.17,1972 [21] Appl. No.; 244,677

[30] Foreign Application Priority Data May 20, 1971 Israel 36925 [52] U.S. Cl. 209/330., 209/365 C [5l] Int. Cl B07b 1/36 [58] Field 0f Search 20g/330, 336, 349, 347, 209/365 C, 334, 44, 437, 443, 446, 471, 382

[56] l References Cited UNITED STATES PATENTS 557,172 3/1896 Symons 209/33 UX 651,006 6/1900 Curtis, 209/437 X 749,578

1/1904 Porter; 209/330 145] July 23, 1974 821,430 5/1906 Perry 209/349 941,862 11/1909 Dibert 209/330 1,330,371 2/1920 Griswold 209/349 X 1,380,289 5/1921 Childers 209/330 l1,541,887 6/1925 Wullstein 209/349 X 1,779,202 10/1930 Winston 209/356 C X 2,001,756 5/1935 Woock 209/44 FOREIGN PATENTS OR APPLICATIONS 110,977 11/1917 Great Britain 209/443 Primary Examiner-Robert Halper Attorney, Agent, or Firm-Browdy and Neimark [5 7 ABSTRACT i Device for the classification of solid objects of the oscillating screen type. In operation the oscillating screen is gradually pulled down against the action of springy means. From the lowermost -position the` screen is released and receives an upward thrust which is abruptly interrupted .by stop means, whereby the screen is unclogged.

2 Claims, 8 Drawing Figures I OSCILLATING SCREEN The present invention concerns a mechanical,oscillating screen, for the classification of `solid objects.

In conventional oscillating screens the screen oscillates during operation in a horizontal or inclined plane. Because of the irregular shape of the objects to be classified some of the objects retained on the screen get.

stuck in the meshes thereof so that the screen tends to be clogged. In known oscillating screens the amount of objects that are stuck in the meshesris reduced by applying a higher frequency of oscillation than is required for optimal passage of particles. In this way, however, the efficiency of the screen is reduced since the higher the frequency of oscillation, the lower becomes the probability that an object of proper size registers with a mesh so as to pass therethrough. Moreover, an increase ofthe frequency of oscillation brings about only a partial solution of the clogging problem. Because of this it is common practice to apply in addition means for unclogging the screen, e.g. brushing, periodically imparting shocks to the sieve'by means of hammers or bouncing balls acting from below,and thelike.

Known oscillating screens are unsatisfactory both because of the fact that they operate at screen oscillation frequencies atwhich ythe efficiency of classification is low and because ofthe additional cumbersome and not always reliable means for unclogging the screen. It is,

therefore, the object of this present invention to provide an improved oscillating screen.

The invention consists in a classification device cornprising an oscillating screen resting on vertically displaceable springy means biasing the screen into its uppermost position, pulling means for gradually pulling the oscillating screen down from its uppermost position against the action of said springy means, means for periodically releasing said pulling means to enable an upward thrust of the screen back lto its uppermost position by the action of `saicl springy means, and stop means for arresting the upward thrust of the screen.

FIG. 5 shows the objects that had been stuck in the screen ejected from the meshes in consequence of the abruptly interruptedupward thrust ofthe screen;

FIG. 6 is a graphical representation of the screen's oscillations;

FIG.r 7 is a graphical characteristic of the simultaneous vertical motion of the screen serving for unclogging; and

FIG. 8 is a graphical representation of efficiency of classification versus the frequency oscillation.

The device according to the invention here illustrated comprises a screen 1 supported by four leaf springs 2 mounted each on a swingable'arm 3 keyed on an axle 4. Underneath screen 1 there may be a tray (not shown) for collecting the objects passing through the screen.

` Screen 1 comprises a pair of depending lugs 5 to each of which is pivotally connected a rod 6 which at its opposite end cooperates with an eccenterwheel 7 keyed on tan axle 8 which through the intermediary of power transmission means 9, 10 is driven by a motor 11. Two swingable arms l2 each journalled ina pair of lugs 13 are each connected by means of areslient rod 14 to screen l. Each arm l2 vcan move up and down, its upward movement being limited by an inverted U- shaped member 15. At its end each arm 12 comprises a follower roller 16 adapted for cooperation with a vcam 17 having acut-out and keyed on an axle v18 equally driven by a motor 11 through the transmission means I0. The entire apparatus is mounted on a frame 20.

During operation'the screen 1 is oscillated through the' action of eccenters 7 and rods 6. Simultaneously therewith, axles 18 and cams 17 are revolved and through thecooperation of cams 17 with follower roller 16, arms 12 are gradually depressed (see FIG. 2) whereby rods 14 are pulled down pulling with them screen 1. During the oscillation ofthe screen the' small The oscillating screen. may be horizontaly or somewhat inclined in order to facilitate the discharge of the retained objects..

In the device according to the invention, the screen performs a composite motion resulting from the combination ofthe oscillations, the periodical gradual downpull and the periodical upward thrust abruptly interruptedby said; stop means. It has been found that'by such combination it becomes possible to operate at a lower oscillation frequency range than in conventional oscillating screens, whereby the efficiency of classification is considerably increased.

The invention is illustratedgby way of example only,

in the accompanying drawings in which:

FIG. 1 is a perspective view of a. device according to the invention;

FIG. 2 is a fragmentaryview of the device of FIG. 1y showing the means for the downpull ofthe screen during the pull; i

FIG. 3 shows objects to be classified on the screen, some being stuck in the meshes, in the operational position of the screen corresponding to the position of the pulling means in` FIG. 2;

FIG. 4 shows the means of FIG. 2 during the release;

ves

size objects pass through while some of the largerones that do not pass through get stuck inthe meshes see the two extreme objects in FIG. 3. j j

. In consequence of the downpull screen 1 is gradually depressed while at the same time continuing its oscillation until each follower roller 16 faces the cut-out of the cooperating cam 17 whereupon arms 12 are released. In consequence of the actions of the leaf springs Zan upward thrust is thereupon imparted to screen 1 andy the upward moving screen pulls abruptly with it rods 14 and arms 12 until the latter are stopped by the web of the associated inverted U-shaped stop members 15. The position of each arm 1'2 and idler roller 16 relative to the cam 17 at the abrupt termination of the above upward thrust of the screen is shown in FIG. 4, and FIG. 5 shows how in consequence the two extreme, large size objects which in FIG. 3 were stuck in the meshes, are now ejected while the smaller objects of FIG. 3" have passed" through the'screen.

The two kinds of movements performed by the i depression occurring during the preponderant part of the cycle, followed by a sudden rise of the screen up to a level slightly above the normal rest level where it is abruptly arrested. It is during the latter part of the cycle that the stuck objects are ejected upwards thereby to clear the meshes in which they got stuck during the first part of the cycle.

The design of the machine according to the invention by which two different periodic movements are combined enables to improve the efficiency of classification to a very substantial extent. This is shown in FIG. 8 in which the efiiciency is plotted against the oscillation frequency of the screen. It is seen from the figure that the classification efficiency rapidly reaches a maximum at low frequency and thereafter drops as the oscillation frequency increases. Notwithstanding this known fact, all known oscillating screens must operate in the frequency range A of FIG. 8 in order to reduce the clogging of the screen to a minimum. Against this, in accordance with the invention it becomes possible for the first time to operate within the range of lower frequency B in which the classification efficiency is near its maximum. Itis obvious from FIG. 8 that the advantage achieved in accordance with the present invention is quite substantial.

It should be noted that the specific design of device described hereinbefore with reference to FIGS. 1, 2 and 4 is only by way of example and that many modifications of design are possible within the basic idea of the present invention. To mention only one example, leaf springs 2 may be replaced by any other springy means, e.g., helical compression springs.

I claim:

l. A classification device comprising:

an oscillating screen having means to oscillate said screen with a substantially horizontal displacement and a substantially harmonic motion, said screen resting on vertically displaceable springy means biasing the screen into its uppermost position;

pulling means for causing a periodical gradual depression of the oscillating screen down from its uppermost position against the action of said springy means;

means for causing a periodical release of said pulling means to enable an upward thrust of the screen back to its uppermost position by the action of said springy means; and

stop means for arresting the upward thrust of the screen, a multiple number of oscillatory cycles of said harmonic motion taking place during each cycle of said periodical depression and release.

2. A classification device comprising:

a screen and means to oscillate said screen at a given cyclical rate with a substantially horizontal displacement;

a vertically displaceable spring means upon which said screen rests, said springy means biasing the screen into its uppermost position; and

means to periodically, at a rate of once for every multiple member of substantially horizontal oscillations, gradually depress said oscillating screen down from its uppermost position against the action of said springy means, and to release said gradual depression to thereby provide an upward thrust of the screen back to its uppermost position by the action of said springy means, said means to periodically gradually depress and release including stop means for arresting the upward thrust of the Patent No.

InventorGS) R011 FELLER Signed `and sealed this (SEAL) Attest:

MCCOY M. GlsoN JR, Attesting Officer UNTTED STATES PATE @ENCE CERT'IMCME fm mmol Dated July 23, 1971+ It is `certified that error appears in the above-identified patent and that said Letters 'Patent are hereby correted as shown below:

Column 4, line 25, "member" should read wnumberfm C@ MARSHALL DANN. Commissioner of Patents FORM PO-105O (1D-69) USCOMM-DC 60376PG9 u,s GOVERNMENT PRINTING OFFICE: |969 o-:1es-334 

1. A classification device comprising: an oscillating screen having means to oscillate said screen with a substantially horizontal displacement and a substantially harmonic motion, said screen resting on vertically displaceable springy means biasing the screen into its uppermost position; pulling means for causing a periodical gradual depression of the oscillating screen down from its uppermost position against the action of said springy means; means for causing a periodical release of said pulling means to enable an upward thrust of the screen back to its uppermost position by the action of said springy means; and stop means for arresting the upward thrust of the screen, a multiple number of oscillatory cycles of said harmonic motion taking place during each cycle of said periodical depression and release.
 2. A classification device comprising: a screen and means to oscillate said screen at a given cyclical rate with a substantially horizontal displacement; a vertically displaceable spring means upon which said screen rests, said springy means biasing the screen into its uppermost position; and means to periodically, at a rate of once for every multiple member of substantially horizontal oscillations, gradually depress said oscillating screen down from its uppermost position against the action of said springy means, and to release said gradual depression to thereby provide an upward thrust of the screen back to its uppermost position by the action of said springy means, said means to periodically gradually depress and release including stop means for arresting the upward thrust of the screen. 